Step-by-step device for a ratchet-wheel

ABSTRACT

A step-by-step drive device for a ratchet-wheel acting through a pawl. The device comprises a coil wound on a cylindrical cupshaped member displaceable in a magnetic field produced by a fixed ferrite core with a cylindrical armature. A clearance of several microns is determined by a toroidal ring of low-friction and low-density material. A damping member is interposed between the closed end of the cup-shaped member and the circular front surface of the cylindrical armature. The pawl may be directly connected to the cup-shaped member or through a weighted lever having one arm connected to the pawl and the other connected to the closed end of the cup-shaped member.

United States Patent [191 Forest STEP-BY-STEP DEVICE FOR ARATCHET-WI-IEEL [75] Inventor: Edmond Forest,'

Saint-Nicolas-DAliermongfrance [73] Assignee: Societe Anonyme: ReveilsBayard,

Saint-Nicolas DAliermont, France 221 Filed: July 27,1973 21 Appl. No.:383,064

[30] Foreign Application Priority Data [111 3,869,930 1 Mar. 11, 1975Primary Examiner-Wesley S. Ratliff, Jr. Attorney, Agent, orFirm-Baldwin, Wight & Brown 57 1 ABSTRACT I A step-by-step drive devicefor a ratchet wheel acting through a pawl. The device comprises a coilwound on a cylindrical cup-shaped member displaceable in a magneticfield produced by a fixed ferrite core with a cylindrical armature. Aclearance of several microns is determined by a'toroidal ring oflow-friction and lowdensity material. A damping member is interposedbetween the closed end of the cup-shaped member and the circular frontsurface of the cylindrical armature. The pawl may be directly connectedto the cupshaped member or through a weighted lever having one armconnected to the pawl and the other connected to the closed end of thecup-shaped member.

10 Claims, 3 Drawing Figures Great Britain 74/128 1 STEP-BY-STEP DEVICEFOR A RATCHET-WHEEL BACKGROUND OF THE INVENTION pawl. A step-by-steprotary motor is also known which associates one or more pair of polescreating a greater or lesser step per revolution. The first of thesedevices has the disadvantage of a low efficiency, and the second is verycomplicated.

SUMMARY OF THE INVENTION The following device avoids the abovedrawbacks.

An object of the present invention is a.step by-step drive device for aratchet-wheel acting through a pawl, comprising a coil connected to asource of electric pulses and wound on a movable cylindrical cup-shapedmember, the closed end of the cup-shaped support being connected to thepawl, a cylindrical armature with a fixed ferrite core engaging saidcup-shaped member, said ferrite core forming an annular magnetic fieldsurrounding the said coil, a guide member for the cup-shaped supportformed as a toroidal ring of lowfriction low-density material formingone piece with the cup-shaped member and defining a clearance of severalmicrons with said cylindrical armature, a damping member interposedbetween the closed end of the cup-shaped member and the circularfront'surface of the cylindrical armature and a spring for returning thecup-shaped member to its rest position.

Such a device combines a high electro-magnetic efficiency with thesimplicity of a ratchet-wheel.

BRIEF DESCRIPTION OF THE DRAWING Other features and advantages willbecome apparent from the description two embodiments ofthe above devicegiven merely-by way of example with reference to the accompanyingdrawing, in which:

FIG. 1 is a schematic showing of a first embodiment v ofthe step-by-stepdrive device for a ratchet-wheel ac- DESCRIPTION OF PREFERREDEMBODIMENTS A The device of FIG. 1 comprises a ratchet-wheel 1 driven bya pawl 2 which is by one end fixed to the closed end 3 of acylindricalcup-shaped member 4.

The other end of the pawl 2 slides in a bearing 5 and cooperates with afixed abutment 6.

' The cup-shaped member 4 carries an aluminum coil 7 connected to asource of electric pulses (not shown). The cup-shaped member 4 is fittedon to a cylindrical carbon steel armature 8 connected by a suitablebridging portion 9 to an annular ferrite core 10 to the coil 7.

Between the bridging portion 9 of the ferrite core 10 and the end of thecup-shaped member 4 a spiral spring 11 is arranged coaxially with thecup-shaped member.

Such a spring which is preferably of nickel silver is shown in moredetail in FIG. 2.

' At the open end of the cup-shaped member and on the interior surfacethereof is provided a toroidal ring guide member 12 formed oflow-friction low-density material. Between the guide member 12, and thearmature 8 is a clearance of several microns.

Finally, a Neoprene R pad fixed to the circular front face of thearmature 8 protrudes towards the closed end 3 of the cup-shaped memberand acts as a damping member for the cup-shaped member 4.

With each electric pulse received by the coil 7 which is placed in themagnetic field provided by the radially magnetized ferrite core 10, thecup-shaped member is attracted towards the armature 8 until the closedend 3 of the cup-shaped member comes into contact with the bumper pad13. In addition to the damping effect due to the pad 13, there is adamping effect due to the air contained in the cup-shaped member 4during the sliding of the latter. When the pulse stops, the spring 11returns the cup-shaped member and the pawl 2 to the position shown inFIG. 1 where the end of the pawl 2 comes in contact with the abutment 6.

In the device of FIG. 3, the parts similar to those shown in FIG. 1 areprovided with the same, but primed numerals. In this embodiment, theradial magnetic field surrounding the coil 7' is obtained by a ferritecore 15 forming one piece with the armature 8 a cup-shaped member 16 isassociated with the ferritecore 15 and another cup-shaped member 4 isreceived inside the cup-shaped member 16. A weighted lever 17 isinterposed between the pawl 2 and the closed end 3' of the cup-shapedmember 4. The weighted lever 17 is adapted to pivot about a fixed pivot18. One of the arms ofthe lever 17 carries a counterweight 19 and isconnected to the pawl 2' the other arm is connected by a link 20 to theclosed end 3 of the cup-shaped member. Finally, a spring 21corresponding to the return spring 11 of the device of FIG. 1 is biasedto return the weighted lever 17 to its centered position.

The device of FIG. 3 is shown in its rest position, i.e., in the absenceof pulses applied to the coil.

The two devices described above are characterized by an axial clearanceof the pawl (2 or 2) defined by the abutments and therefore by theimpossibility of turning the ratchet wheel 1 or 1' one or more teeth asis possible with known step-by-step drive devices.

Finally, with a device according to the invention an optimum efficiencywhile establishing the characteristics of the spiral spring 21 or of theelastic diaphragm 11 so that the period of the electric pulses is inproportion to the period of vibration of the coil and its movableassembly.

The device according to the invention may be used in situation in whichdisplacements proportional to the number of electric pulses is to beobtained. The invention is particularly applicable to clock and watchmaking, especially quartz-crystal watches and clocks.

The invention is of course not limited to the disclosed embodiments buton the contrary covers all alternatives within the scope of the appendedclaims.

What is claimed is:

1. A step-by-step drive device for a ratchet-wheel acting through apawl, said drive device comprising a movable cylindrical cup-shapedmember having a closed end mechanically connected to the pawl, a coilconnected to a source of electric pulses wound on said movablecup-shaped member, a cylindrical armature of a fixed ferrite corereceived in said cup-shaped member,'said ferrite core forming an'annularmagnetic field surrounding said coil, a combined guide member andsealing'ring for the cup-shaped member formed as a [toroidal] ring oflow-friction[,] low-density material fixed to the cup-shaped member anddefining a clearance of several microns between the cylindrical armaturearid the [cup-shaped] combined guide member andsealing ring, said.combined guide member and sealing ring together with said cup-shapedmember and said ferrite core defining a pneumatic dampening means forsaid cup-shaped member, a damping member interposed between the closedend of the cupshaped member[,] and the circular front surface of thecylindrical armature, and resilient means for returning the cup-shapedmember to its rest position.

2. A device according to claim 1, wherein the ferrite core is annularand produces the magnetic field surrounding the cup-shaped member, saidpawl being fixed directly to the closed end of the cup-shaped member,and further comprising a bearing associated with an abutment, saidresilient means being formed as an elastic diaphragm [such as a spiralspring mounted] coaxially with and [out-side] outside the cup-shapedmember between the cup-shaped member and the [armature] ferrite core.

3. A device according to claim 1, wherein the pawl is connected to theclosed end of the cup-shaped member through a weighted lever, one arm ofthe weighted lever being connected to the pawl and the other arm of theweighted lever being connected to the closed end of the cup-shapedmember, said weighted lever having a counter-balancing weight, theresilient means being arranged to return the weighted .lever to itscentered position.

. 4. A device according to claim 3 wherein said weighted lever hasathirdarm, and said resilient means beingconnected to said third arm.

5. A device according to claim 3 wherein the operative effect of saidresilient means on the movable components of said device provides themovable components with a vibration frequency generally correspondingwith the frequency of the electric pulses.

6. A device according to claim 2 where the operative effect of saidresilient means on the movable components of said device provides themovable components with a vibration frequency generally correspondingwith the frequency of the electric pulses.

7. A device according to claim 2 wherein said resilient means is aspiral spring.

8. A device according to claim 2 wherein said resilient means is aspiral spring, said spring including inner and outer annular rings, andspiral elements joining together said rings.

9. A device according to claim 1 wherein said resilient means isa spiralspring, said spring including inner and outer annular rings, and spiralelements joining together saidrings.

10. A device according to claim 1 wherein the operative effect of saidresilient means on the movable components of said device provides themovable components with a vibration frequency generally correspondingwith the frequency of the electric pulses.

1. A step-by-step drive device for a ratchet-wheel acting through apawl, said drive device comprising a movable cylindrical cup-shapedmember having a closed end mechanically connected to the pawl, a coilconnected to a source of electric pulses wound on said movablecup-shaped member, a cylindrical armature of a fixed ferrite corereceived in said cup-shaped member, said ferrite core forming an annularmagnetic field surrounding said coil, a combined guide member andsealing ring for the cup-shaped member formed as a ring of low-frictionlowdensity material fixed to the cup-shaped member and defining aclearance of several microns between the cylindrical armature and thecombined guide member and sealing ring, said combined guide member andsealing ring together with said cup-shaped member and said ferrite coredefining a pneumatic dampening means for said cup-shaped member, adamping member interposed between the closed end of the cup-shapedmember and the circular front surface of the cylindrical armature, andresilient means for returning the cup-shaped member to its restposition.
 1. A step-by-step drive device for a ratchet-wheel actingthrough a pawl, said drive device comprising a movable cylindricalcup-shaped member having a closed end mechanically connected to thepawl, a coil connected to a source of electric pulses wound on saidmovable cup-shaped member, a cylindrical armature of a fixed ferritecore received in said cup-shaped member, said ferrite core forming anannular magnetic field surrounding said coil, a combined guide memberand sealing ring for the cup-shaped member formed as a ring oflow-friction low-density material fixed to the cup-shaped member anddefining a clearance of several microns between the cylindrical armatureand the combined guide member and sealing ring, said combined guidemember and sealing ring together with said cup-shaped member and saidferrite core defining a pneumatic dampening means for said cup-shapedmember, a damping member interposed between the closed end of thecup-shaped member and the circular front surface of the cylindricalarmature, and resilient means for returning the cup-shaped member to itsrest position.
 2. A device according to claim 1, wherein the ferritecore is annular and produces the magnetic field surrounding thecup-shaped member, said pawl being fixed directly to the closed end ofthe cup-shaped member, and further comprising a bearing associated withan abutment, said resilient means being formed as an elastic diaphragmcoaxially with and outside the cup-shaped member between the cup-shapedmember and the ferrite core.
 3. A device according to claim 1, whereinthe pawl is connected to the closed end of the cup-shaped member througha weighted lever, one arm of the weighted lever being connected to thepawl and the other arm of the weighted lever being connected to theclosed end of the cup-shaped member, said weighted lever having acounter-balancing weight, the resilient means being arranged to returnthe weighted lever to its centered position.
 4. A device according toclaim 3 wherein said weighted lever has a third arm, and said resilientmeans being connected to said third arm.
 5. A device according to claim3 wherein the operative effect of said resilient means on the movablecomponents of said device provides the movable components with avibration frequency generally corresponding with the frequency of theelectric pulses.
 6. A device according to claim 2 wherein the operativeeffect of said resilient means on the movable components of said deviceprovides the movable components with a vibration frequency generallycorresponding with the frequency of the electric pulses.
 7. A deviceaccording to claim 2 wherein said resilient means is a spiral spring. 8.A device according to claim 2 wherein said resilient means is a spiralspring, said spring including inner and outer annular rings, and spiralelements joining together said rings.
 9. A device according to claim 1wherein said resilient means is a spiral spring, said spring includinginner and outer annular rings, and spiral elements joining together saidrings.